Storage device for reliably maintaining data in a reproducible state for a long period of time

ABSTRACT

A time counting device, a cache memory and a copy control circuit are added to a conventional disk drive so that recorded information is copied periodically and automatically. Alternatively, a cache memory, a copy control circuit, a reference control circuit, a first time counting device and a second time counting device are added to the conventional disk drive so that information which remains recorded for a predetermined period of time after its last recording date is automatically copied. According to another embodiment, a reference signal is recorded in advance and a reproduced output is periodically measured. If the reproduced output is lower than a reference value, recorded information is automatically copied. Other embodiments are also disclosed with the aim of ensuring that information recorded on a magnetic media can always be reproduced reliably, even in the case of high density recording.

This is a continuation application of U.S. Ser. No. 09/989,026, filedNov. 21, 2001 U.S. Pat. No. 6,437,931; which is a continuationapplication of U.S. Ser. No. 09/712,148, filed Nov. 15, 2000, now U.S.Pat. No. 6,404,571; which is a continuation application of U.S. Ser. No.09/564,633, filed May 3, 2000, now U.S. Pat. No. 6,243,221; which is acontinuation application of U.S. Ser. No. 09/300,428, filed Apr. 28,1999, now U.S. Pat. No. 6,084,729; which is a continuation applicationof U.S. Ser. No. 08/811,570, filed Mar. 5, 1997, now U.S. Pat. No.5,923,485.

FIELD OF THE INVENTION

The present invention relates to a method for maintaining thereliability of a storage device and, more particularly, to a storagedevice capable of holding high-density recorded information in asemi-permanently reproducible state.

BACKGROUND OF THE INVENTION

An example of a disk drive control system known in the art isillustrated in FIG. 5 along with a portion of the control system of ahost computer. In FIG. 5, reference numeral 25 denotes a control circuitsystem of the disk drive, and reference numeral 21 denotes part of thecontrol system of the host computer. This disk drive control system 25includes an interface section 4, a read/write control section 5, a headposition control section 6, and a spindle motor control section 7. Theinterface section 4 is connected to the read/write control section 5,the head position control section 6, the spindle motor control section7, and a disk drive interface section 11 in the host computer 21. Inaddition, the read/write control section 5, the head position controlsection 6 and the spindle motor control section 7 are respectivelyconnected to a read/write head 8, a head carriage 9 and a spindle motor10. An instruction from the host computer 21 is sent to the interfacesection 4 of the disk drive control system 25 through the disk driveinterface section 11 in the host computer 21, so that reading/writing ofinformation is performed. When reading/writing is performed, a disk isrotated by the spindle motor 10. Then, the read/write head 8 is moved toa desired track by head carriage 9 so that the formation and detectionof recorded magnetization can be performed by the read/write head 8.These operations are respectively controlled by the spindle motorcontrol section 7, the head position control section 6 and theread/write control section 5. A disk drive having the above-describedtype of arrangement is disclosed in, for example, “Transistor TechnologySpecial, The whole Technique for Utilizing Hard Disks and SCSI, p. 8 (CQPublishing Company).

Once information is recorded in a conventional disk drive, theinformation is not copied as long as a person does not give the diskdrive a specific instruction to copy. This is because magnetic recordinghas been considered to be a recording method that is capable ofsemi-permanently holding information recorded once, in the form ofrecorded magnetization.

However, if magnetic particles are reduced in size or a medium is madefrom a thin film in order to increase the recording density of magneticrecording, the recorded magnetization of each bit will weaken with time,due to influences such as from thermal fluctuation. It has beendiscovered that this phenomenon is particularly serious at hightemperatures. This is disclosed in the Journal of Applied Physics 75(10) (May 1994), IEEE Transactions on Magnetics, Vol. 30, No. 6, (1994),and the Technical Report of the Institute of Electronics, Informationand Communication Engineers of Japan, MR94-105, pp. 25-30 (March, 1995)”and so on.

In IEEE Transactions on Magnetics, Vol. 32, No. 1, (January 1996), it isreported that in the case of a medium using a soft magnetic under layer,the reproduced output may decrease with time. A decrease in recordedmagnetization leads to the problem that the reliability of the storagedevice is impaired because information cannot be correctly reproduced.

The process of conducting a self-diagnosis and predicting trouble(SMART) has been proposed as a means for maintaining or improving thereliability of a disk drive. According to this process, a warning isissued to a host if the number of seek errors or retries during normaluse exceeds a reference value. This process is disclosed in DATAQUESTALERT (Apr. 17, 1995). However, in this method, since no warning isissued until an abnormality occurs during normal use, there is a riskthat it will be too late to securely restore data when recordedmagnetization of the medium has become small.

SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention is to solve the above-describedproblems of the prior art and hold high-density recorded information ina semi-permanently reproducible state, thereby maintaining thereliability of storage devices.

To achieve this object, a storage device according to the presentinvention has at least one recording medium, a medium driving sectionfor driving the recording medium, a read/write head for reading/writinginformation from/to the recording medium, a head positioning section fordriving the read/write head, and a control system for processing arecording signal to be sent to a write head and a reproduced signal sentfrom a read head, and for processing a control signal for the mediumdriving section and the head positioning section. The storage deviceadditionally includes a time counting device, a cache memory and a copycontrol circuit, and periodically and automatically copies informationrecorded in the storage device.

More specifically, in the embodiment shown in FIG. 1, a disk driveincludes at least an interface section 4, a read/write control section5, a head position control section 6 and a spindle motor control section7, each of which is connected to the interface section 4, a read/writehead 8 connected to the read/write control section 5, a head carriage 9connected to the head position control section 6, and a spindle motor 10connected to the spindle motor control section 7. The storage deviceadditionally includes a first timing counting device 1, a cache memory 2and a copy control circuit 3, the copy control circuit 3 is connected toeach of the timing counting device 1, the cache memory 2, the interfacesection 4, the read/write control section 5, the head position controlsection 6 and the spindle motor control section 7, and the disk driveperiodically transmits from the timing counting device 1 a signal foractuating the copy control circuit 3, sequentially reproducinginformation previously recorded in the disk drive, temporarily storingthe information in the cache memory 2, and again automatically recordingthe information into the disk, i.e. performing copying.

A storage device according to the present invention includes at leastone recording medium, a medium driving section for driving the recordingmedium, a read/write head for reading/writing information from/to therecording medium, a head positioning section for driving the read/writehead, and a control system for processing a recording signal to be sentto a write head and a reproduced signal sent from a read head, and forprocessing a control signal for the medium driving section and the headpositioning section. The storage device additionally includes a timecounting device, a cache memory, a copy control circuit and a referencecontrol circuit, and has a function to automatically copy informationwhich remains recorded for a predetermined time after the last recordingdate on which arbitrary information has been recorded, from theinformation previously recorded in the storage device.

Specifically, in the embodiment shown in FIG. 2, a disk drive at leastcomprises an interface section 4, a read/write control section 5, a headposition control section 6, a spindle motor control section 7, each ofthe three sections 5, 6 and 7 being connected to the interface section4, a read/write head 8 connected to the read/write control section 5, ahead carriage 9 connected to the head position control section 6, and aspindle motor 10 connected to the spindle motor control section 7. Thestorage device additionally includes a cache memory 2, a copy controlcircuit 3, a reference control circuit 12, a first time counting device13 and a second time counting device 14, the copy control circuit 3 isconnected to each of the cache memory 2, the interface section 4, theread/write control section 5, the head position control section 6, thespindle motor control section 7 and the reference control circuit 12,the reference control circuit 12 is connected to each of the interfacesection 4, the read/write control section 5, the head position controlsection 6, the spindle motor control section 7, the first time countingdevice 13 and the second time counting device 14, the storage device hasa function to periodically transmit a signal for actuating the referencecontrol circuit 12 from the first time counting device 13, search forinformation which remains recorded for a predetermined time or moreafter the last recording date, in the information previously recorded inthe disk drive, while making reference to the present year, month andday outputted from the second time counting device 14, transfer the nameof the information to the copy control circuit 3, sequentially reproducethe corresponding information, temporarily store the information in thecache memory 2 and thereafter again automatically record the storedinformation in the disk drive, i.e. performing copying.

A storage device according to the present invention includes at leastone recording medium, a medium driving section for driving the recordingmedium, a read/write head for reading/writing information from/to therecording medium, a head positioning section for driving the read/writehead, and a control system for processing a recording signal to be sentto a write head and a reproduced signal sent from a read head, and forprocessing a control signal for the medium driving section and the headpositioning section. The storage device additionally includes a timecounting device, a cache memory, a copy control circuit and a reproducedoutput detect circuit, and records a predetermined signal in part of thestorage device in advance, periodically measures the reproduced outputof the signal and, if the reproduced output is smaller than apredetermined reference value, again record the signal, andautomatically copying information recorded in the storage device.Specifically, in the embodiment shown in FIG. 3, a disk drive at leastcomprises an interface section 4, a read/write control section 5, a headposition control section 6, a spindle motor control section 7, each ofthe three sections 5, 6 and 7 being connected to the interface section4, a read/write head 8 connected to the read/write control section 5, ahead carriage 9 connected to the head position control section 6, and aspindle motor 10 connected to the spindle motor control section 7. Thestorage device additionally includes a cache memory 2, a copy controlcircuit 3, a time counting device 13 and a reproduced output detectcircuit 17, the copy control circuit 3 is connected to each of the cachememory 2, the interface section 4, the read/write control section 5, thehead position control section 6, the spindle motor control section 7 andthe reproduced output detect circuit 17, the reproduced output detectcircuit 17 is connected to each of the read/write control section 5, thehead position control section 6, the spindle motor control section 7 andthe time counting device 13, and has a function to record apredetermined reference signal in part of the disk drive in advance,periodically transmit from the first time counting device 13 a signalfor actuating the reproduced output detect circuit 17, measure thereproduced output of the reference signal, and, if the reproduced outputis smaller than a predetermined reference value, transmit from thereproduced output detect circuit 17 a signal for actuating the copycontrol circuit 3, again record the reference signal, and automaticallycopying information recorded in the disk device 23.

Any of the above storage devices according to the present invention alsohave a function to automatically copy information recorded in thestorage device to the storage device or to another storage device if thetemperature in the storage device is higher than a predeterminedreference value. These storage devices further include a thermometer anda time counting device, and has a function to automatically copy theinformation recorded in the storage device to the storage device or toanother storage device at intervals of period shorter than that duringnormal temperature if the temperature in the storage device is higherthan the predetermined reference value.

For example, in the embodiment shown in FIG. 4 in which this method isadded to the embodiment shown in FIG. 1, a disk drive at least comprisesan interface section 4, a read/write control section 5, a head positioncontrol section 6, a spindle motor control section 7, each of the threesections 5, 6 and 7 being connected to the interface section 4, aread/write head 8 connected to the read/write control section 5, a headcarriage 9 connected to the head position control section 6, and aspindle motor 10 connected to the spindle motor control section 7, andis characterized in that the storage device additionally comprises afirst timing counting device 1, a cache memory 2, a copy control circuit3, a thermometer 18 and a second time counting device 19, the copycontrol circuit 3 is connected to each of the first timing countingdevice 1, the cache memory 2, the interface section 4, the read/writecontrol section 5, the head position control section 6, the spindlemotor control section 7, the thermometer 18 and the second time countingdevice 19, the disk drive has, in addition to the function toperiodically and automatically copy information, a function to measurethe temperature in the disk drive with the thermometer 18 at all timesduring the operation of the disk drive and, if the temperature is higherthan a predetermined reference value, transmit from the thermometer 18 asignal for actuating the second time counting device 19, transmit fromthe second time counting device 19 a signal for actuating the copycontrol circuit 3 at intervals of period shorter than that during normaltemperature, and automatically copy information recorded in the diskdevice to the disk drive or another disk drive.

These and other objects, features and advantages of the presentinvention will become more apparent in view of the following detaileddescription of the preferred embodiments in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one embodiment of a storage devicecontrol system according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the storagedevice control system according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of the storagedevice control system according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the storagedevice control system according to the present invention.

FIG. 5 is a block diagram showing an example of a conventional storagedevice control system.

FIGS. 6(a) and 6(b) are schematic arrangement views showing oneembodiment of a disk drive provided with the storage device controlsystem according to the present invention. FIG. 6(a) is a plan view andFIG. 6(b) is a cross-sectional view taken along line 6 b—6 b of FIG.6(a).

FIG. 7 is a characteristic graph showing the dependence of thestandardized reproduced output on the elapsed time at normaltemperature, for comparison of the characteristic of the disk driveprovided with the storage device control system according to the presentinvention shown in FIG. 1 with the characteristic of a conventionalexample. Characteristic line “a” shows the results obtained by carryingout measurement of one example of the disk drive control systemaccording to the present invention and characteristic line “b” shows theresults obtained by carrying out measurement of the conventionalexample. Dashed line “c” shows the minimum reproduced output valuerequired of the disk drive.

FIG. 8 is a characteristic graph showing the dependence of standardizedreproduced output on the elapsed time in a 60° C. atmosphere, forcomparison of the characteristic of the disk drive provided with thestorage device control system according to the present invention shownin FIG. 4 with the characteristic of a conventional example.Characteristic line “d” shows the results obtained by carrying outmeasurement of one example of the disk drive control system according tothe present invention and characteristic line “e” shows the resultsobtained by carrying out measurement the conventional example. Dashedline “c” shows the minimum reproduced output value required of the diskdrive.

FIG. 9 illustrates an example of a time counting device of the presentinvention.

FIG. 10 illustrates an example of a cache memory and a copy controlcircuit of the present invention.

FIG. 11 illustrates an example of a reference control circuit of thepresent invention.

FIG. 12 illustrates another example of a time counting device of thepresent invention.

FIG. 13 illustrates yet another example of a time counting device of thepresent invention.

FIG. 14 illustrates an example of a reproduced output detect circuit ofthe present invention.

FIG. 15 illustrates an example of a thermometer employed according tothe present invention.

FIG. 16 illustrates another example of a time counting device of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a storage device to which the present invention isapplied will be described below in more detail with reference to theaccompanying drawings.

FIG. 1 is a view showing a disk drive control system according to oneembodiment of the present invention. In FIG. 1, reference numeral 20denotes a disk drive control system. This disk drive control system 20includes a time counting device 1, a cache memory 2, a copy controlcircuit 3, an interface section 4, a read/write control section 5, ahead position control section 6, and a spindle motor control section 7.The copy control circuit 3 is connected to each of the timing countingdevice 1, the cache memory 2, the interface section 4, the read/writecontrol section 5, the head position control section 6 and the spindlemotor control section 7. The interface section 4 is connected to each ofthe read/write control section 5, the head position control section 6and the spindle motor control section 7. The read/write control section5, the head position control section 6 and the spindle motor controlsection 7 are respectively connected to a read/write head 8, a headcarriage 9 and a spindle motor 10.

Normally, a read/write operation is carried out in a manner similar tothe conventional example. First, a disk is rotated by the spindle motor10, then the read/write head 8 is moved to a desired track by the headcarriage 9, and then the formation and detection of recordedmagnetization are performed by the read/write head 8. These operationsare respectively controlled by the spindle motor control section 7, thehead position control section 6 and the read/write control section 5.

In addition to the above-described normal operations, each time one yearelapses after the present disk drive is manufactured, it sequentiallyreproduces all existing files, temporarily stores the reproducedinformation in the cache memory 2, and again records that informationinto the same area on the disk. The timing counting device 1 is actuatedwhen the present disk drive is manufactured, and each time one yearelapses, the timing counting device 1 transmits a signal for actuatingthe copy control circuit 3, to automatically perform the above-describedoperation. It should be noted that while one year has been set as thetime period, other time periods can be selected while being within thescope of the present invention.

The present embodiment differs from the conventional example shown inFIG. 3 in that the arrangement of the present embodiment is such thatthe timing counting device 1, the cache memory 2 and the copy controlcircuit 3 are added to the conventional disk drive control system, andthe present embodiment has a function to periodically transmit from thetiming counting device 1 a signal for actuating the copy control circuit3, sequentially reproducing information previously recorded in the diskdrive, temporarily storing the information in the cache memory 2, andagain automatically recording the information into the disk, that is, afunction to perform copying. Incidentally, the timing counting device 1and the cache memory 2 may be similar to existing types, and the copycontrol circuit 3 may consist of only a section which is required tocontrol copying in an existing disk controller. Further description ofsome of the elements is provided later in the description.

One example of the disk drive provided with the disk drive controlsystem 20 of the present embodiment will be described below withreference to FIGS. 6(a) and 6(b). FIGS. 6(a) and 6(b) are schematicarrangement views of one embodiment of the disk drive according to thepresent invention, where FIG. 6 (a) is a plan view and FIG. 6(b) is across-sectional view taken along line 6 b—6 b of FIG. 6(a). In theseFigures, reference numeral 15 denotes a recording medium, for example adisk which uses Co sputtered medium, reference numeral 10 denotes aspindle motor which rotationally drives the recording medium 15,reference numeral 8 denotes a read/write head for reading/writing asignal from/to the recording medium, reference numeral 9 denotes a headcarriage, which is called a rotary actuator, for moving the read/writehead 8 above the recording medium in the radial direction thereof, andreference numeral 20 denotes a disk drive control system. A plurality ofrecording media are secured to the spindle motor 10, and the read/writeheads 8 are respectively provided on both sides of each of the recordingmedia.

The PRML method is used for reproduced waveform signal processing inthis disk drive, and a servo track positioning method is used forpositioning the read/write head 8. The magnetic characteristics of therecording medium 15 which uses a Co sputtered medium are such that theproduct of the remnant magnetization by the magnetic film thickness is70 Gauss·μm and its circumferential coercivity is 3,000 Oe, and therotational speed of the spindle motor is 7,200 rpm. The read/write head8 uses an inductive head as a write head and a magneto-resistive head asa read head. The track width and the gap length of the write head are1.3 μm and 0.4 μm, respectively. The track width and the gap length ofthe read head are 1.1 μm and 0.2 μm, respectively. The recording densityis 5 Gbits/in².

In FIG. 7, line “a” shows the results obtained by measuring thedependence of standardized reproduced output on the elapsed time atnormal temperature during the use of the disk driving arranged in thismanner. Line “a” is obtained by measuring the reproduced outputimmediately after a signal is recorded into the disk drive of thepresent embodiment, subsequently leaving the disk drive alone with nooperation conducted by the host side, again measuring the reproducedoutput on a later day, and comparing this reproduced output with thevalue measured immediately after the recording. FIG. 7 further shows acharacteristic graph “b” of a conventional disk drive. A dashed line “c”shows the minimum reproduced output value required of the disk drive tobe used as a product. As can be seen from FIG. 7, the reproduced outputof the conventional disk drive becomes lower with the passage of timeand, one and a half year later, falls below the minimum value requiredof the disk drive to be used as a product. On the other hand, the diskdrive of the present embodiment keeps its reproduced output higher thanin the conventional example, thereby improving reliability.

Although, in the present embodiment, information is re-recorded atintervals of period of one year, the period may be determined to be adifferent value according to the specifications of the read/write systemand to the magnetic characteristics and the thermal stability of thedisk. Although, in the present embodiment, information is copied to thesame location where the information has been recorded, such informationmay be copied to a different location in the same disk drive or toanother storage device. In addition, while the above-describedperiodical automatic copy operation is being performed, a message to theeffect that “periodical automatic copying is being executed” may be sentto the host side.

Alternatively, the above-described automatic copy function may be addedto the host computer.

FIG. 2 is a schematic block diagram of a second embodiment of a diskdrive control system according to the present invention. In FIG. 2,reference numeral 22 denotes a disk drive control system. In FIG. 2,identical reference numerals are used to denote constituent sectionsidentical to those shown in FIG. 1, and the detailed description thereofwill be omitted in order to be more concise. Specifically, the diskdrive control system of the present embodiment includes a conventionaldisk drive control system to which a cache memory 2 and a copy controlcircuit 3 are added, and also includes a reference control circuit 12, afirst time counting device 13 and a second time counting device 14. Thecopy control circuit 3 is connected to each of the cache memory 2, theinterface section 4, the read/write control section 5, the head positioncontrol section 6, the spindle motor control section 7 and the referencecontrol circuit 12. The reference control circuit 12 is connected toeach of the interface section 4, the read/write control section 5, thehead position control section 6, the spindle motor control section 7,the first time counting device 13 and the second time counting device14. The arrangement of the second embodiment differs from that of thefirst embodiment in that the first time counting device 13 transmits asignal for actuating the reference control circuit 12, at intervals of30 days. Also, information which was recorded one year or more ago issearched for, using the present year, month and day outputted from thesecond time counting device 14 as a reference. The identification ofsuch information which is found is transferred to the copy controlcircuit 3 and the corresponding information is sequentially reproduced.The information is stored temporarily in cache memory 2 before beingcopied and again stored in the same area on the disk. The cache memory2, the first time counting device 13 and the second time counting device14 which are additionally provided may be the same as existing ones, andthe copy control circuit 3 and the reference control circuit 12 mayconsist of only sections which are required to control their respectivefunctions in an existing disk controller.

The dependence of the standardized reproduced output with respect totime, at normal temperature, was measured with the control system 22 ofthe present embodiment employed in place of the disk drive controlsystem 20 used in the disk drive shown in FIG. 6. The results of themeasurement are equivalent to those of Embodiment 1 shown in FIG. 7. Itcan be understood, therefore, that the disk drive having the arrangementof the present embodiment is also affective in maintaining a highreliability.

Although, in the present embodiment, the last recording date of theexisting file is checked at intervals of period of 30 days and the timein which it is judged that information needs to be again recorded is oneyear, these periods may be set to different values according to thespecifications of the read/write system and the magnetic characteristicsand thermal stability of a disk. Although, in the present embodiment,information is copied to the same location where the information hasbeen recorded, such information may be copied to a different location inthe same disk drive or to another storage device. In addition, while theabove-described periodical automatic copy operation is being performed,a message to the effect that “periodical automatic copying is beingexecuted” may be sent to the host side.

Alternatively, the above-described automatic copy function may be addedto the host computer.

FIG. 3 is a schematic block diagram of a third embodiment of the controlsystem of the disk drive according to the present invention. In FIG. 3,reference numeral 23 denotes a disk drive control system. Identicalreference numerals are used to denote portions identical to those ofEmbodiment 1 shown in FIG. 1, and a detailed description thereof will beomitted for conciseness. Specifically, the disk drive control system ofthe present embodiment includes a conventional disk drive control systemto which a cache memory 2 and a copy control circuit 3 are added, andalso includes a time counting device 13 and a reproduced output detectcircuit 17. The copy control circuit 3 is connected to each of the cachememory 2, an interface section 4, a read/write control section 5, a headposition control section 6, a spindle motor control section 7 and thereproduced output detect circuit 17. The reproduced output detectcircuit 17 is connected to each of the read/write control section 5, thehead position control section 6, the spindle motor control section 7 andthe time counting device 13. The arrangement of embodiment 3 differsfrom that of embodiment 1 in that a predetermined reference signal isrecorded in part of the disk device in advance, and the time countingdevice 13 transmits a signal for actuating the reproduced output detectcircuit 17, at intervals of 30 days, and the reproduced output detectcircuit 17 measures the reproduced output of the reference signal and,if the measured value of the reproduced output is smaller than thepredetermined reference value, transmits a signal for actuating the copycontrol circuit 3. In the present embodiment, a value equal to 0.85times the standardized reproduced output is set as the reference value.After the copy control circuit 3 is actuated, the reference signal isagain recorded, and information recorded in the disk drive issequentially reproduced and temporarily stored in the cache memory 2,and the information is again recorded into the same area on the disk.The cache memory 2 and the time counting device 13 may be similar toexisting ones, and the copy control circuit 3 and the reproduced outputdetect circuit 17 may consist of only sections which are required tocontrol their respective functions in an existing disk controller or inthe read/write control section. Details of various components arediscussed further herein by way of example.

The dependence of the standardized reproduced output on the elapsed timeat normal temperature was measured with the control system 23 of thepresent embodiment being employed in place of the disk drive controlsystem 20 used in the disk drive shown in FIG. 6. The results of themeasurement are equivalent to those of Embodiment 1 shown in FIG. 7. Itcan be understood, therefore, that the disk drive having the arrangementof the present embodiment is also effective in maintaining highreliability.

Although, in the present embodiment, the reproduced output of thereference signal is checked at intervals of period of 30 days and thereference value of the reproduced output is equivalent to 0.85 times thestandardized reproduced output, these periods may be set to differentvalues according to the specifications of the read/write system and themagnetic characteristics and thermal stability of the disk. In addition,each time the disk drive is actuated, the operation of checking thereproduced output of the reference signal may be performed. Furthermore,although information is copied to the same location where theinformation has been recorded, such information may be copied to adifferent location in the same disk drive or to another storage device.In addition, while the above-described periodical automatic copyoperation is being performed, a message to the effect that “periodicalautomatic copying is being executed” may be sent to the host side.

Alternatively, the above-described automatic copy function may be addedto the host computer.

FIG. 4 is a schematic block diagram of a fourth embodiment of the diskdrive control system according to the present invention. In FIG. 4,reference numeral 24 denotes a disk drive control system. Identicalreference numerals are used to denote portions identical to those ofEmbodiment 1 shown in FIG. 1, and the detailed description thereof willbe omitted for conciseness. Specifically, the disk drive control systemof the present embodiment includes a conventional disk drive controlsystem to which a first timing counting device 1, a cache memory 2 and acopy control circuit 3 are added, and also includes a thermometer 18 anda second time counting device 19. The copy control circuit 3 isconnected to each of a first timing counting device 1, the cache memory2, a interface section 4, a read/write control section 5, a headposition control section 6, a spindle motor control section 7 and thesecond time counting device 19. The thermometer 18 is connected to thesecond time counting device 19. The disk drive control system accordingto this embodiment periodically and automatically performs copying ofinformation, as described previously in connection with the firstembodiment, but differs from the first embodiment in that thethermometer 18 measures the temperature in the disk drive during theoperation of the disk drive at all times and, if the temperature ishigher than 60° C., transmits a signal for actuating the second timecounting device 19. The second time counting device 19, after beingactuated, transmits a signal for actuating the copy control circuit 3,at intervals of six months, thereby automatically copying informationrecorded in the disk drive to the same or a different disk drive. Afterthe copy control circuit 3 is actuated, the information recorded in thedisk drive in sequentially reproduced and temporarily stored in thecache memory 2, and the information is again recorded. Incidentally, thefirst timing counting device 1, the cache memory 2, the thermometer 18and the second time counting device 19 may be of existing types, and thecopy control circuit 3 may consist of only the sections which arerequired to control the copy function in an existing disk controller.

The dependence of the standardized reproduced output with respect totime, at normal temperature, was measured with the control system 24 ofthe present embodiment employed in place of the disk drive controlsystem 20 used in the disk drive shown in FIG. 6. The results of themeasurement are equivalent to that for the first embodiment 1, shown inFIG. 7. In addition, a similar measurement was separately conducted inan atmosphere having a temperature of 60° C. A characteristic graph “d”which represents the results of this measurement is shown in FIG. 8.FIG. 8 further shows a characteristic graph “e” of a conventional diskdrive. The dashed line “c” shows the minimum reproduced output valuerequired of the disk drive to be used as a product. As can be seen fromFIG. 8, the reproduced output of the conventional disk drive becomeslower with the passage of time and, one year later, falls below theminimum value required of the disk drive to be used as a product. On theother hand, the disk drive of the present embodiment keeps itsreproduced output higher than that of the conventional disk drive.

It can be understood, therefore, that the disk drive having thearrangement of the present embodiment is also effective in maintaining ahigh reliability at a high temperature of approximately 60° C.

In the present embodiment, the temperature at which the thermometer 18transmits a signal for actuating the second time counting device 19 isset to 60° C. and the second time counting device 19 transmits a signalfor actuating the copy control circuit 3, at intervals having a periodof 6 months. However, the period may be set to a different valueaccording to the specifications of the read/write system and to themagnetic characteristics and thermal stability of the disk. In addition,although, in the present embodiment, the thermometer 18 and the secondtime counting device 19 are added to the first embodiment, they may alsobe added to either of the second and third embodiments. Furthermore,although information is copied to the same location where theinformation has been recorded, such information may be copied to adifferent location in the same disk drive or to another storage device.In addition, while the above-described periodical automatic copyoperation is being performed, a message to the effect that “periodicalautomatic copying is being executed” may be sent to the host side.

Alternatively, the above-described automatic copy function may be addedto the host computer.

FIGS. 9-16 are more detailed examples of various components added by thepresent invention to the conventional device. These detailed examplesare provided as additional disclosure only and are not to be construedas the only implementations of these components. Of course, minor,insignificant variations can be made and still be within the scope ofthe present invention.

FIG. 9 illustrates a time counting device 1. The last date when copycontrol circuit 3 was used is recorded in memory 33. Complement circuit32 is provided when this information is stored in binary. Apredetermined time period, such as one year, is recorded as a thresholdfor causing copy control circuit 3 to start, and is stored in memory 35.The result calculated in full adder 34 is compared with that stored inmemory 35 in comparator 36. If more than a year has passed since thelast day the copy control circuit 3 was at work, comparator 36 puts outa signal, output 60, to make the copy control circuit 3 start, andmemory controller 37 makes memory 33 record the present date as anexpression in the binary scale. For the fourth embodiment discussedabove, input 73 is connected with thermometer 18.

FIG. 10 illustrates a cache memory 2 and copy control circuit 3. Copycontrol processor 38 puts out a signal to copy the information recordedin storage device by way of R/W format control unit 39, series/paralleltransducer 40 and error correct code producer/checker 41. Output 61 andoutput 62 are connected with Read/Write control section 5. Output 63 isconnected with both head position control section 6 and spindle motorcontrol section 7. R/W format control unit 39, series/paralleltransducer 40 and error correct code producer/checker 41 are shown in“Transistor Technology Special, The Whole Technique for Utilizing HardDisks and SCSI, pg. 8 (CQ Publishing Company). When the informationrecorded in the storage device is forwarded, cache memory 2 is used astemporary storage.

FIG. 11 illustrates reference control circuit 12. Reference controlprocessor 42 puts out a signal to refer to the last date when eachinformation was written in storage device by way of R/W format controlunit 39, series/parallel transducer 40 and error correct codeproducer/checker 41. Output 67 and output 68 are connected withRead/Write control section 5. Output 69 is connected with both headposition control section 6 and spindle motor control section 7. Input 64is connected with time counting device 13. The signal to start referencecontrol processor is received from time counting device 13. Input 65 andoutput 66 are connected with the time counting device 14. Theinformation of the last date when each information was written instorage device is sent from output 66 to time counting device 14. Thesignal whether more than one year has passed since the last day theinformation was written or not comes from time counting device 14 toinput 65. Output 60 is connected with copy control circuit 2. If morethan one year has passed since the last day the information was written,the signal to start copy control circuit is sent from output 60.

FIG. 12 illustrates a time counting device 13. Time counting device 13is the same as time counting device 1 except the information recorded inmemory 43 and except that output 64 is connected with either referencecontrol circuit 12 or reproduced output detect circuit 17. In memory 43,a time period equal to 30 days is recorded, for example.

FIG. 13 illustrates a time counting device 14. Output 65 and input 66are connected with reference control circuit 12. The last date when theinformation recorded in storage device was written is sent fromreference control circuit 12 to input 66. The time difference betweenthis date and the present date shown by clock 31 is calculated in fulladder 34. The time period, one year, is previously recorded in memory 33as a threshold beyond which copy control circuit 3 is started. Theresult calculated in full adder 34 is compared with memory 33 incomparator 36. If more than a year has passed since the last day whenthe information was written in storage device, the signal to make theinformation copied is sent from output 65 by way of reference controlcircuit 12 to copy control circuit 3.

FIG. 14 illustrates a reproduced output detect circuit 17. Reproducedoutput detect control processor 44 puts out a signal to detect thevoltage of the reproduced output of the information recorded fordetection in a storage device by way of R/W format control unit 39,series/parallel transducer 40 and error correct code producer/checker41. Output 70 and output 71 are connected with Read/Write controlsection 5. Output 72 is connected with both head position controlsection 6 and spindle motor control section 7. The voltage (Vr) is setto be equal to 0.85 times the voltage of the standardized reproducedoutput as a threshold for starting the copy control circuit 3. Thereproduced output is sent by way of DA converter 45 to analog comparatorand is compared with the voltage Vr. Output 60 is connected with copycontrol circuit 3. If the reproduced output is lower than Vr, reproducedoutput detect control processor 44 outputs a signal to rewrite theinformation recorded for detection in a storage device, and puts out thesignal from output 60 to make copy control circuit 3 started.

FIG. 15 illustrates a thermometer 18. The value of 60 degrees centigradeis previously recorded in memory 50 as a threshold past with the copycontrol circuit 3 is started. The value of temperature that is measuredby thermometer 48 is compared with memory 50 in comparator 36. Outputs73 and 74 are connected with time counting devices 1 and 19,respectively. If the temperature is lower than 60 degrees centigrade,time counting device 1 is started and time counting device 19 isstopped. If the temperature is higher than 60 degrees centigrade, timecounting device 1 is stopped and time counting device 19 is started.

FIG. 16 illustrates time counting device 19. Time counting dedvice 19 isas same as time counting device 1 except for the information recorded inmemory 52. In memory 52, information corresponding to a time period of 6months is recorded. Input 74 is connected with thermometer 18. Output 60is connected with copy control circuit 3.

According to the present invention, information recorded in a recordingmedium is again recorded before the recorded magnetization formed in therecording medium decreases to a value at which the recorded informationbecomes difficult to reproduce without error. This way, informationrecorded at high density can be held in a semi-permanently reproduciblestate and the reliability of the storage device can be maintained.

While the present invention has been described above in connection withthe preferred embodiments, one of ordinary skill in the art would beenabled by this description to make various modifications and still bewithin the scope and spirit of the present invention as recited in theappended claims.

What is claimed is:
 1. A magnetic storage device comprising: at leastone magnetic medium, at least one magnetic head, and a disk drivecontrol system including a thermometer which measures temperature,wherein said disk drive control system instructs the magnetic head toread information recorded on the medium, and to write the informationthat is read to the medium, when the temperature measured by thethermometer exceeds a preset threshold value.
 2. A magnetic storagedevice according to claim 1, further comprising: another storage deviceconnected to said storage device, wherein said disk drive control systeminstructs the magnetic head to write the information that is read tosaid another storage device instead of said medium of said storagedevice.
 3. A magnetic storage device according to claim 1, wherein saiddisk drive control system instructs the magnetic head to write theinformation that is read to the same track on the medium from which itwas read.
 4. A magnetic storage device according to claim 1, whereinsaid disk drive control system instructs the magnetic head to write theinformation that is read to another medium.
 5. A magnetic storage deviceaccording to claim 1, further comprising: a cache memory for temporarilystoring the information read by the magnetic head.
 6. A magnetic storagedevice comprising: at least one magnetic medium, at least one magnetichead, means for measuring temperature, and means for controlling themagnetic head, wherein said disk drive control system instructs themagnetic head to read information recorded on the medium, and to writethe information that is read to the medium, when the temperaturemeasured by the thermometer exceeds a preset threshold value.
 7. Amagnetic storage device according to claim 6, further comprising:another storage device connected to said storage device, wherein saiddisk drive control system instructs the magnetic head to write theinformation that is read to said another storage device instead of saidmedium of said storage device.
 8. A magnetic storage device according toclaim 6, wherein said disk drive control system instructs the magnetichead to write the information that is read to the same track on themedium from which it was read.
 9. A magnetic storage device according toclaim 6, wherein said disk drive control system instructs the magnetichead to write the information that is read to another medium.
 10. Amagnetic storage device according to claim 6, further comprising: acache memory for temporarily storing the information read by themagnetic head.